1. Field of the Invention
The present invention relates, in general, to a valve for precisely metering or intermittently feeding precise quantities of material. More particularly, the present invention relates to a metering valve adapted to simultaneously carry out two functions within the valve, namely, a first function consisting of metering a precise quantity of material into one port of the valve, and a second function consisting of dispensing a premeasured quantity of material from a second port in the valve.
2. Discussion of the Prior Art
Metering valves of this type are utilized, amongst other applications, for the intermittent feeding of predetermined quantities or charges of material into a chemical stream at a controlled rate which is determined by the rotational speed of the valve plug. Valves having this general type of construction are known in the art, and usually are of the plug type wherein a single orifice of a predetermined size extends through the valve plug perpendicular to the axis of rotation of the latter. The valve plug is adapted to assume two separate positions, one placing the orifice in communication with a source of material which is to be metered, and the second placing it in a position to feed the previously metered material into a controlled chemical reaction. Valves of this nature have found particular utility in polymerization reactors wherein precise quantities or charges of a metered material, such as a catalyst, must be directed into the chemical reactor, and particularly reactors employed for the polymerization of ethylene into polyethylene. These prior art valves require a 90.degree. rotational displacement between filling and discharge positions, and a rotational movement of 180.degree. for each complete operative cycle.
Solvik et al U.S. Pat. No. 3,227,312 discloses an improvement over that type of plug valve. In particular, Solvik et al disclose a plug valve of the shot injecting or feeding type, which operates twice as fast as the prior type of plug valves, by requiring only a 90.degree. rotation of the valve plug for each operative cycle, in contrast with a 180.degree. valve plug rotation necessary in the earlier prior art valve technology. Thus, in Solvik et al a cylindrical valve plug is mounted for rotation in an aperture provided in a valve body. The valve body has first and second sets of radially extending inlet and outlet passageways, with the two sets being disposed perpendicular relative to each other. Two nonintersecting valve ports extend through the valve plug perpendicular to the plug axis of rotation. The centers of the inlets and outlets of both valve ports are located in the same plane perpendicular to the axis of rotation of the valve plug. The passageways do not intersect because each port passageway is inclined or sloped away from the other, with one passageway being inclined in a first direction along the axis of rotation and the second passageway being inclined in the opposite direction along the axis of rotation. However, although a metering valve of this type is capable of operating at substantially twice the speed of operation of earlier prior art metering plug valves, the manufacture of such a valve is relatively complicated and expensive. The forming of the abovementioned ports in the valve plug, one of which inclines in a first direction along the axis of rotation and the second of which inclines or slopes in an opposite direction along the valve plug axis of rotation, results in a valve plug configuration which is both difficult and costly to manufacture, thereby rendering such a construction both expensive and uneconomic from a commercial standpoint. Thus, it becomes desirable to provide a metering valve which incorporates the rapid speed of operation inherent in the Solvik et al plug valve design, but which eliminates the necessity of having a valve configuration which is difficult and expensive to manufacture.